package com.wstuo.common.tools.util;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;

public class Base64 {
	
	 private static final char[] legalChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
	            .toCharArray();
	 /**
	     * data[]进行编码
	     * 
	     * @param data
	     * @return
	     */
	    public static String encode(byte[] data) {
	        int start = 0;
	        int len = data.length;
	        StringBuffer buf = new StringBuffer(data.length * 3 / 2);
	 
	        int end = len - 3;
	        int i = start;
	        int n = 0;
	 
	        while (i <= end) {
	            int d = ((((int) data[i]) & 0x0ff) << 16)
	                    | ((((int) data[i + 1]) & 0x0ff) << 8)
	                    | (((int) data[i + 2]) & 0x0ff);
	 
	            buf.append(legalChars[(d >> 18) & 63]);
	            buf.append(legalChars[(d >> 12) & 63]);
	            buf.append(legalChars[(d >> 6) & 63]);
	            buf.append(legalChars[d & 63]);
	 
	            i += 3;
	 
	            if (n++ >= 14) {
	                n = 0;
	                buf.append(" ");
	            }
	        }
	 
	        if (i == start + len - 2) {
	            int d = ((((int) data[i]) & 0x0ff) << 16)
	                    | ((((int) data[i + 1]) & 255) << 8);
	 
	            buf.append(legalChars[(d >> 18) & 63]);
	            buf.append(legalChars[(d >> 12) & 63]);
	            buf.append(legalChars[(d >> 6) & 63]);
	            buf.append("=");
	        } else if (i == start + len - 1) {
	            int d = (((int) data[i]) & 0x0ff) << 16;
	 
	            buf.append(legalChars[(d >> 18) & 63]);
	            buf.append(legalChars[(d >> 12) & 63]);
	            buf.append("==");
	        }
	 
	        return buf.toString();
	    }
	 
	    public static byte[] decode(String s) {
	 
	        ByteArrayOutputStream bos = new ByteArrayOutputStream();
	        try {
	            decode(s, bos);
	        } catch (IOException e) {
	            throw new RuntimeException();
	        }
	        byte[] decodedBytes = bos.toByteArray();
	        try {
	            bos.close();
	            bos = null;
	        } catch (IOException ex) {
	            System.err.println("Error while decoding BASE64: " + ex.toString());
	        }
	        return decodedBytes;
	    }
	 
	    private static void decode(String s, OutputStream os) throws IOException {
	        int i = 0;
	 
	        int len = s == null ? 0 : s.length();
	 
	        while (true) {
	            while (i < len && s.charAt(i) <= ' ')
	                i++;
	 
	            if (i == len)
	                break;
	 
	            int tri = (decode(s.charAt(i)) << 18)
	                    + (decode(s.charAt(i + 1)) << 12)
	                    + (decode(s.charAt(i + 2)) << 6)
	                    + (decode(s.charAt(i + 3)));
	 
	            os.write((tri >> 16) & 255);
	            if (s.charAt(i + 2) == '=')
	                break;
	            os.write((tri >> 8) & 255);
	            if (s.charAt(i + 3) == '=')
	                break;
	            os.write(tri & 255);
	 
	            i += 4;
	        }
	    }
	 
	    private static int decode(char c) {
	        if (c >= 'A' && c <= 'Z')
	            return ((int) c) - 65;
	        else if (c >= 'a' && c <= 'z')
	            return ((int) c) - 97 + 26;
	        else if (c >= '0' && c <= '9')
	            return ((int) c) - 48 + 26 + 26;
	        else
	            switch (c) {
	            case '+':
	                return 62;
	            case '/':
	                return 63;
	            case '=':
	                return 0;
	            default:
	                throw new RuntimeException("unexpected code: " + c);
	            }
	    }
}
